Session 2 ILOs - Major Blood Vessels and Osteology and radiographic appearance of skull

Question 1

Describe where you would palpate the carotid artery and the jugular venous pulsation

Explain the relevance of this knowledge to clinical practice (e.g. measuring JVP and central line access)

Answer 1

Palpate carotid artery:
- Runs through the carotid triangle (bifurcates at C4)

Palpate jugular venous pulsation:
- Measure height from sternal angle and add 5cm?

Measure jugular venous pressure:

• Internal jugular vein can provide an estimation of right atrial pressure (when the heart contracts, a pressure wave passes upwards, which can be observed)
• Generally use right IJV as it is directly connected to the right atrium

Question 2

Describe the anterior, middle and posterior fossae of the skull base and their boundaries

Answer 2

Anterior fossa:

• Posterior boundary is the lesser wings of the sphenoid bone
• Mostly frontal bone
• Contains crista galli, cribriform plate, orbital plates, ethmoid bone and sphenoid bone

Middle fossa:

• Anterior boundary is lesser wings of sphenoid bone
• Posterior boundary is petrous part of temporal bone
• Contains body and greater wing of the sphenoid, and the squamous and petrous parts of the temporal bone (also pituitary gland

Posterior fossa:

• Anterior boundary is petrous part of temporal bone
• Contains mostly temporal bone and occipital bone
• Importantly the posterior cranial fossa houses the brainstem and cerebellum

Question 3

Describe the major types of fractures that involve the facial skeleton and skull (base/vault), the clinical signs suggestive of these fractures and the potential consequences of such injuries.

Answer 3

Skull fractures:
- Can be linear or comminuted (depressed vs non-depressed)
1. Pterion fracture
- Danger to underlying middle meningeal artery, risk of extradural haemorrhage
2. Basilar fracture (more rare)
- Racoon eyes (periorbital ecchymosis)
If petrous part bone fracture (subtype of basilar fracture)
- Battle’s sign
- Eardum pooling blood
- Blood/CSF out of ear

Facial skeleton fractures - 4 most common types:

1. Nasal fracture – most common facial fracture
   - Often significant soft tissue swelling and associated epistaxis (nose bleed)
2. Maxillary fracture – high-energy trauma
   - Rare, but if they do occur then risk of fragments falling backwards and blocking airways
3. Mandibular fracture – often bilateral
   - Clinical features can include misalignment of the teeth
4. Zygomatic arch fracture
   - Displaced fractures can damage the infraorbital nerve, leading to ipsilateral paraesthesia of the check, nose, and lip

Question 4

Describe the functional anatomy of the temporomandibular joint (TMJ) including the movements and muscles involved

Describe clinical signs and symptoms of TMJ dislocation and TMJ dysfunction

Answer 4

Synovial hinge-type joint between the mandibular fossa of the temporal bone and the mandibular condyle

Superior and inferior joint capsules separated by cartilaginous disc

Superior joint capsule:

• Involved in gliding movement (protraction and retraction)
• Protrusion: lateral pterygoid (plus medial pterygoid)
• Retraction: Temporalis (posterior fibres)

Inferior joint capsule:
- Involved in rotational movement (opening and closing)
Elevation: master, temporalis, medial pterygoid
Depression: lateral pterygoid and gravity

TMJ dislocation and dysfunction:

• Caused by the forward movement of the condyle past the articular tubercle
• Contraction of muscles around the joint keep the joint locked in anterior displacement
• Can occur due to yawning or facial trauma (especially if jaw is open)
• Symptoms include pain and any issues associated with being unable to close jaw i.e. can’t talk

Question 5

Outline the major differences between the fetal/infant and adult skull and describe the location and role of the anterior and posterior fontanelles.

Answer 5

Fetal/infant skull has fontanelles where the sutures of the skull have not ossified (adult skull instead has a Bregma and Lambda)
- Inportant for passage through the birth canal and for growth of the foetal skull
Fetal/infant skull is also smaller due to the lack of growth compared to an adult

Anterior fontanelle:

• Sits in region of the Bregma
• Fuses at approx. 1.5-2 years

Posterior fontanelle:

• Sits in region of the Lambda
• Fuses at approx. 3 months

Question 6

Identify the general course and related anatomy of the common carotid artery

Answer 6

Common carotid artery arises from:

• Right side: occurs after the brachiocephalic trunk splits into the right common carotid and the right subclavian
• Left side: comes directly off the aortic arch

At superior border of the thyroid cartilage (level of C4 and within the carotid triangle) - the common carotid arteries divide into the internal and external carotid arteries (prior to this, the right common carotid gives off a brach of the inferior thyroid artery to the thyroid)

There is a bulge at the site of bifurcation - carotid sinus (can be used for carotid sinus massage to reduce tachycardia)

Bifurcation is also a common site of atherosclerosis

Question 7

Identify the general course and related surface anatomy of th internal and external jugular vein

Answer 7

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Question 8

Identify the general course of the internal carotid artery - including the branches it gives off

Answer 8

Bifurcation of the common carotid artery occurs around C4

Internal carotid artery doesn’t give off any branches until it enters base of the skull (via the foramen magnum)

Carotid canal is within the petrous part of the temporal bone turns medially and horizontally forming an ‘S’ shaped bend

Gives off 4 branches:

• Opthalmic artery (divides into supratrochlear and supraorbital)
• Anterior cerebral artery
• Middle cerebral artery
• Posterior communicating artery

Question 9

Identify the branches given off by the external carotid artery

Answer 9

Gives off 8 branches:

(some anatomists like freaking out poor medical students)

Superior thyroid
Ascending pharyngeal
Lingual
Facial
Occipital
Posterior auricular
Maxillary (terminal branch)
Superficial temporal (terminal branch and can be involved in giant cell arteritis)

Question 10

Identify the 5 arteries that supply the scalp (branches of both the internal and external carotid)

Answer 10

Internal carotid artery:
- Supratrochlear and Supraorbital (branches of Opthalmic artery)

External carotid artery:

• Occipital
• Posterior auricular
• Superficial temporal

Question 11

Outline the 5 layers of the SCALP

Answer 11

SCALP!

Skin
Connective tissue (contains blood vessels)
Aponeurosis
Loose areolar tissue
Periosteum

Question 12

Identify the general course and related anatomy of the internal jugular vein

Answer 12

The internal jugular vein is a continuation of the sigmoid sinus (which drains superior sagittal sinus, inferior sagittal sinus, traverse sinus)

The vein exits the skull via the jugular foramen

The internal jugular vein descends within the carotid sheath, deep to the sternocleidomastoid muscle and lateral to the common carotid artery

IJV combines with the subclavian vein to form the brachiocephalic vein

Question 13

Identify the general course and related anatomy of the external jugular vein

Answer 13

Supplies majority of the external face:

Formed by the union of two veins:

1. Posterior auricular vein – drains the area of scalp superior and posterior to the outer ear.
2. Retromandibular vein (posterior branch) – itself formed by the occipital and superficial temporal veins

The external jugular vein then descends down the neck within the superficial fascia, runs anteriorly to the sternocleidomastoid muscle, crossing it in an oblique, posterior–inferior direction

The vein passes underneath the clavicle and terminates by draining into the subclavian vein